Field of the Invention
The present invention relates to a display unit including an organic EL (electro luminescence) device.
Description of the Related Art
In recent years, in the field of display units for displaying images, display units including as a light emitting device of a pixel, a current drive type optical device with the light emitting luminance changeable according to the flowing current value such as an organic EL device have been developed, and such display units are facilitated to be commercialized (for example, refer to Japanese Unexamined Patent Application Publication No. 2008-083272).
The organic EL device is a self-light emitting device differently from a liquid crystal device or the like. Thus, a display unit (organic EL display unit) including the organic EL device does not need a light source (backlight). Accordingly, in the organic EL display unit, compared to a liquid crystal display unit necessary for a light source, the image visibility is high, the electric power consumption is low, and the device response rate is high.
Drive systems in the organic EL display unit include simple (passive) matrix system and active matrix system as in the liquid crystal display unit. The former system has a disadvantage that it is difficult to realize a large and high definition display unit, though its structure is simple. Thus, currently, the active matrix system has been actively developed. In such a system, a current flowing through a light emitting device arranged for every pixel is controlled by an active deice provided in a drive circuit provided for every light emitting device (in general, TFT (Thin Film Transistor)).
FIG. 15 illustrates a schematic structure of a general organic EL display unit. A display unit 100 illustrated in FIG. 15 includes a display section 110 in which a plurality of pixels 120 are arranged in a matrix state and a drive section for driving each pixel 120 (a horizontal drive circuit 130, a writing scanning circuit 140, and a power source scanning circuit 150).
Each pixel 120 is composed of a red-use pixel 120R, a green-use pixel 120G, and a blue-use pixel 120B. As illustrated in FIG. 16 and FIG. 17, the pixels 120R, 120G, and 120B are composed of an organic EL device 121 (organic EL devices 121R, 121G, and 121B) and a pixel circuit 122 connected thereto. FIG. 16 illustrates a circuit structure of the pixels 120R, 120G, and 120B. FIG. 17 illustrates a layout of the pixels 120R, 120G, and 120B.
The pixel circuit 122 is composed of a sampling-use transistor Tws, a retentive capacity Cs, and a drive-use transistor TDr, and has a circuit structure of 2Tr1C. A gate line WSL drawn from the writing scanning circuit 140 is extended in the row direction, and is connected to a gate 123A of the transistor Tws through a contact 126A.
A drain line DSL drawn from the power source scanning circuit 150 is also extended in the row direction, and is connected to a drain 124C of the transistor TDr through a leading wiring 128A. Further, a signal line DTL drawn from the horizontal drive circuit 130 is extended in the column direction, and is connected to a drain 123C of the transistor Tws through a contact 126B and a leading wiring 128B. A source 123B of the transistor TWS is connected to a gate 124A of the drive-use transistor TDr and an end of the retentive capacity Cs (terminal 125A) through a contact 126C. A source 124B of the transistor TDr and the other end of the retentive capacity Cs (terminal 125B) are connected to an anode 127A of the organic EL device 121 through a contact 126D. A cathode 127B of the organic EL device 121 is connected to an external cathode line CTL.